Driver circuit for providing constant voltage to an auxiliary circuit

ABSTRACT

A driver circuit receiving wireless communication over a wireless network is disclosed. The driver circuit includes a lighting load, a main driver, and an auxiliary driver. The lighting load is selectively illuminated based on an output voltage being provided to the lighting load that is at least a forward voltage of the lighting load. The wireless communication is indicative of whether the lighting load is to be illuminated. The main driver is for controlling current and voltage within the driver circuit such that if the wireless communication indicates the lighting load is to be illuminated, then the current delivered to the lighting load is regulated by the main driver, and if the wireless communication indicates the lighting load is not to be illuminated, then the output voltage delivered to the lighting load is controlled by the main driver is below the forward voltage.

TECHNICAL FIELD

The present disclosure relates generally to a driver circuit forproviding constant power, and more particularly to a driver circuit fora lighting load that provides substantially constant DC voltage to anauxiliary circuit without the need for dedicated power circuitry.

BACKGROUND

Wireless lighting control systems may utilize radio frequency (RF)communication to communicate control signals to an antenna elementmounted in a lighting fixture. For example, a user may turn on, turnoff, or dim a light using wireless control. A wireless lighting fixturetypically includes a main driver as well as a micro control unit(MCU)/radio. The main driver may be used to control the load for dimmingand color control, as well as to turn the wireless lighting fixture ONand OFF, and the MCU/radio may be used to facilitate wirelesscommunication of the lighting fixture.

Power consumption has always been a consideration in RF networks. Withwireless control, when the light fixture is turned ON the MCU/radio isin receive mode and therefore requires power. Furthermore, if thelighting fixture is turned OFF, and there is no power being delivered tothe lighting load, then the MCU/radio is in standby mode. However, theMCU/radio still requires power when in standby mode. Thus, it isappreciated that the MCU/radio requires a low voltage power supply atall times, regardless of whether the lighting fixture is ON or OFF.Therefore, it may be challenging to produce a lighting fixture with RFcapability at low cost with direct communication between the main driverand the MCU/radio. It may also be challenging to supply power to theMCU/radio without the need for dedicated circuitry, which add cost andcomplexity to the lighting fixture. Thus, there exists a continuing needin the art for a lighting fixture with an improved control scheme forsupplying continuous power to the MCU/radio.

SUMMARY

In one embodiment, a driver circuit receiving wireless communicationover a wireless network is disclosed. The driver circuit includes alighting load, a main driver, and an auxiliary driver. The lighting loadis selectively illuminated based on an output voltage being provided tothe lighting load that is at least a forward voltage of the lightingload. The wireless communication is indicative of whether the lightingload is to be illuminated. The main driver is for controlling currentand voltage within the driver circuit such that if the wirelesscommunication indicates the lighting load is to be illuminated, then thecurrent delivered to the lighting load is regulated by the main driver,and if the wireless communication indicates the lighting load is not tobe illuminated, then the output voltage delivered to the lighting loadis controlled by the main driver is below the forward voltage. Theauxiliary driver requires a substantially constant DC voltage, and is incommunication with the main driver. The auxiliary driver receives thewireless communication over the wireless network, where the drivercircuit provides the substantially constant DC voltage at all operatingconditions.

In another embodiment, a driver circuit receiving wireless communicationover a wireless network is disclosed. The driver circuit includes alighting load, a main driver, and an auxiliary driver. The lighting loadis selectively illuminated based on an output voltage being provided tothe lighting load that is at least a forward voltage of the lightingload. The wireless communication is indicative of whether the lightingload is to be illuminated. The main driver is for controlling voltagewithin the driver circuit such that if the wireless communicationindicates the lighting load is to be illuminated, then the outputvoltage provided to the lighting load is at least the forward voltage,and if the wireless communication indicates that the lighting load isnot to be illuminated, then the voltage delivered to the lighting loadis below the forward voltage. The auxiliary driver requires asubstantially constant DC voltage, and is in communication with the maindriver. The auxiliary driver receives the wireless communication overthe wireless network, where the driver circuit provides thesubstantially constant DC voltage at all operating conditions.

In yet another embodiment, a driver circuit receiving wirelesscommunication over a wireless network includes a lighting load, aswitch, a network that selectively generates an overvoltage value, amain driver, and an auxiliary driver. The lighting load is selectivelyilluminated based on an output voltage being provided to the lightingload that is at least a forward voltage of the lighting load. Thewireless communication is indicative of whether the lighting load is tobe illuminated. The main driver includes a plurality of inputs, and isin communication with the switch and the network. The main driver andincludes control logic for causing the switch to operate in burstpackets at a burst mode in response to receiving the overvoltage valuefrom the network. The main driver controls voltage to the lighting loadsuch that if the wireless communication indicates the lighting load isnot to be illuminated, then the forward voltage is not provided to thelighting load. The auxiliary driver requires a substantially constant DCvoltage, and is in communication with the main driver. The auxiliarydriver receives wireless communication over a wireless network. Theauxiliary driver includes control logic for monitoring the wirelessnetwork for an OFF signal. The auxiliary driver includes control logicfor inducing a switching signal at one of the plurality of inputs of themain driver in response to receiving the OFF signal over the wirelessnetwork. In response to receiving the switching signal, the main driverincreases a frequency of the burst packets to a threshold frequency togenerate the constant DC voltage required by the auxiliary driver duringburst mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary block diagram of a wireless lighting fixturehaving a driver circuit, where the driver circuit includes a main driverand a micro control unit (MCU)/radio;

FIG. 2 is an exemplary circuit diagram of the driver circuit shown inFIG. 1, during a first stroke of operation;

FIG. 3 is an exemplary circuit diagram of the driver circuit shown inFIG. 1, during a second stroke of operation;

FIG. 4 is an alternative embodiment of the driver circuit shown in FIG.1;

FIG. 5 is yet another embodiment of the driver circuit shown in FIG. 1;and

FIG. 6 is an exemplary process flow diagram illustrating a method ofproviding constant low voltage DC power to the MCU/radio shown in FIG.1.

DETAILED DESCRIPTION

The following detailed description will illustrate the generalprinciples of the invention, examples of which are additionallyillustrated in the accompanying drawings. In the drawings, likereference numbers indicate identical or functionally similar elements.

FIG. 1 is an exemplary block diagram of a driver circuit 10 for drivinga lighting load 12. In one exemplary embodiment, the driver circuit 10may be part of a wireless lighting fixture 14. As explained in greaterdetail below, the lighting fixture 14 may be connected to a wirelessnetwork 16 that allows for an individual to turn the lighting fixture 14ON and OFF and dim the lighting load 12 as well by manipulating a userinput device 17. The lighting load 12 may include one or more lightemitting diodes (LEDs), which are illustrated in FIGS. 2-3. However, itis to be understood that other types of lighting elements may be usedfor the lighting fixture 14 as well such as, for example, compactfluorescent lamps (CFLs) and halogen lighting. The driver circuit 10 mayinclude a pair of power input lines 20 for connection to a source of ACpower 18 such as, for example, main power lines at nominal 120 or 230volts AC. The driver circuit 10 may also include a fuse 22 (FIG. 2), avaristor such as a metal-oxide varistor (MOV) 24 (FIG. 2), a rectifier26, an electromagnetic interference (EMI) filter 28, a low pass filter30, a main driver 32, a second driver that is illustrated as a microcontrol unit (MCU)/radio 34, a transformer 36, a converter 38, and avoltage regulator 40.

As explained in greater detail below, the disclosed driver circuit 10provides substantially constant DC voltage (e.g., 3.3 volts) to theMCU/radio 34 without dedicated circuitry, even if the lighting fixture14 is turned OFF and the lighting load 12 is no longer illuminated toproduce visible light. It should be understood that in one embodimentthe MCU/radio 34 may be duty-cycled part of the time in receive modewhen the lighting fixture 14 is ON, however substantially constant DCvoltage still encompasses this approach. Furthermore, although anMCU/radio 34 is shown in the figures, it is to be understood that thisillustration is merely exemplary in nature and the disclosure should notbe limited to supplying constant DC voltage to an MCU/radio. Thedisclosed driver circuit 10 may be used to provide constant DC voltageto any other type of secondary or auxiliary circuit requiring constantDC voltage as well such as, for example, a sensor network for sensingambient light, or bias circuitry.

Referring to both FIGS. 1 and 2, the input lines 20 of the drivercircuit 10 may be connected to the rectifier 26. The rectifier 26converts incoming AC power from the source of AC power 18 to a pulsingDC power. Although the rectifier 26 is shown in FIG. 2 as a full wavediode bridge rectifier, any other type of full wave rectifier may beused as well. The output of the rectifier 26 may be connected to the EMIfilter 28. As seen in FIG. 2, in one non-limiting example the EMI filter28 may include an inductor L1 connected to two capacitors C1 and C2. Theoutput of the EMI filter 28 may be referred to as a bus voltage +B ofthe driver circuit 10. The low pass filter 30 may receive the busvoltage +B. In the embodiment as shown in FIG. 2, the low pass filter 30is a passive low pass filter including a resistor R1 and a capacitor C3,however it is to be understood that this configuration is exemplary innature and any number of passive components may be used. Those ofordinary skill in the art will appreciate that the resistor R1 is apull-up resistor. As seen in FIG. 2, the low pass filter 30 is connectedto power supply pin (V_(CC)), which is also referred to as a power inputpin 50. The low pass filter 30 is also connected to a GATE pin 52 of themain driver 32.

The main driver 32 may refer to, be part of, or include an electroniccircuit, a combinational logic circuit, a field programmable gate array(FPGA), a processor (shared, dedicated, or group) that executes code,other suitable components that provide the described functionality, or acombination of some or all of the above, such as in a system-on-chip.The term module may include memory (shared, dedicated, or group) thatstores code executed by the processor. The term code, as used above, mayinclude software, firmware, microcode, or assembly code and may refer toprograms, routines, functions, classes, or objects. One commerciallyavailable example of the main driver 32 is integrated circuit (IC) modelnumber SSL5235, which is commonly used for LED dimming control, and isavailable from NXP B. V., of Eindhoven, the Netherlands. However, it isto be understood that any other IC for regulating the current andcontrolling the voltage to the lighting load 12 may be used as well.

Continuing to refer to FIG. 2, the main driver 32 may also include otherinputs or pins as well, such as a loop compensation pin 54 (COMP), adrain pin 56 (DRAIN), an overvoltage protection pin 58 (DEMOV), a dimpin 60 (DIM), and a ground current sense pin 62 (ISNS). In oneembodiment, the loop compensation pin 54 (COMP) of the main driver 32 isconnected to a floating ground G_(F) through a capacitor C4, and theground current sense pin 62 of the main driver 32 is connected to thefloating ground G_(F) by a sense resistor R2.

Although FIGS. 1 and 2 illustrate the main driver 32 connected to thefloating ground G_(F), it is to be understood that this illustration ismerely exemplary in nature, and the main driver 32 may be connected to acommon ground G of the driver circuit 10 as well. Similarly, the MCU 34is illustrated in the figures as connected to the floating ground G_(F)as well (i.e., the main driver 32 and the MCU/radio 34 both share thesame ground, which is the floating ground G_(F).) However, it is to beunderstood that the MCU/radio 34 may be connected to the common ground Gof the driver circuit as well. In one embodiment, the main driver 32 maybe connected to the floating ground G_(F), and the MCU/radio 34 may beconnected to the common ground G. Alternatively, in another embodimentthe main driver 32 may be connected to the common ground G, and theMCU/radio 34 may be connected to the floating ground G_(F).

The drain pin 56 may receive the bus voltage +B of the driver circuit10. The drain pin 56 represents a drain of a switch 31 (FIG. 1). In theexemplary embodiment as shown in FIG. 1, the switch 31 is ametal-oxide-semiconductor field-effect transistor (MOSFET) that islocated within the main driver 32. While a MOSFET is described, theswitch 31 is not limited to only a MOSFET, and other types of switchesor transistors such as, for example, a bipolar junction transistor (BJT)may be used as well. Moreover, although the present disclosure describesthe switch 31 integrated within the main driver 32, the switch 31 may beexternal to the main driver 32 as well, where the main driver 32 mayinclude control logic or circuitry for driving an external switch. Onecommercially available example of an IC for driving an external switchis model number SSL5231 available from NXP B.V., of Eindhoven, theNetherlands.

Delivering power to the power input pin 50 of the main driver 32 will inturn activate or turn on the main driver 32. Once the main driver 32 isactivated, this allows the main driver 32 to operate in switching mode,where the switch 31 (FIG. 1) of the main driver 32 switches between anopen and closed position. As seen in FIG. 2, once the main driver 32 isactivated, and the driver circuit 10 may operate at a first stroke wherecurrent from the bus voltage +B of the driver circuit 10 may flow out ofthe drain pin 56 of the main driver 32. During the first stroke, theswitch 31 of the main driver 32 is closed. This allows for the currentreceived at the drain pin 56 of the main driver 32 to exit the maindriver 32 through the ground current sense pin 62.

The current exiting the ground current sense pin 62 may flow through thesense resistor R2 to the converter 38. In the embodiment as shown inFIG. 2, the converter 38 is a buck/boost converter including thetransformer 36. The transformer 36 has a primary side winding T1A andsecondary side winding T1B. The converter 38 also includes a flyback orfreewheeling diode D1. In one exemplary embodiment, the freewheelingdiode D1 is a Schottky diode. Although a buck/boost converter isillustrated, those skilled in the art will appreciate that other typesof voltage step down converters may be used as well such as for example,flyback converters, a buck converter, or a boost converter. The currentflowing from the sense resistor R2 flows through the primary sidewinding T1A of the transformer 36 during the first stroke, therebyincreasing the current in the primary side winding T1A from zero.

The converter 38 may be used to provide current to the lighting load 20during a second stroke of the driver circuit 10. During the secondstroke, the switch 31 (FIG. 1) of the main driver 32 is open. Thus,current flowing into the drain pin 56 of the main driver 32 may not flowout of the main driver 32 through the ground current sense pin 62. Theflow of current through the driver circuit 10 during the second strokeis illustrated in FIG. 3. Turning now to FIG. 3, during the secondstroke current may flow from the primary side winding T1A to a capacitorC5. The capacitor C5 may be used to reduce or substantially eliminateany ripple from the output of the converter 38. The current may thenflow out of the capacitor C5 and to the lighting load 12. The currentmay flow out of the lighting load 12 through the freewheeling diode D1,and back to the ground current sense pin 62 of the main driver 32. Thecurrent in the primary side winding T1A now approaches zero. Once thecurrent is about zero, a new switching cycle may begin, and the switch31 of the main driver 32 is closed.

Continuing to refer to FIG. 3, the voltage regulator 40 may include thesecondary side winding T1B of the converter 38, a diode D3 arranged inseries with the secondary side winding T1B, a linear voltage regulator70, and capacitors C6 and C7 arranged in parallel with one another. Thevoltage regulator 70 may be used to produce the constant DC voltagesupplied to the MCU/radio 34. In one exemplary embodiment, the constantDC voltage supplied to the MCU/radio 34 may be about 3.3 volts, howeverit is to be understood that this value is merely exemplary in nature.Those of ordinary skill in the art will readily understand that othervoltage values may be provided as well, depending on the specificrequirements of the MCU/radio 34.

The number of turns on the secondary side winding T1B may be adjusted inorder to step down the voltage from the primary side winding T1B of theconverter 38 before the voltage from the primary side winding T1B issent to the linear voltage regulator. For example, in one embodiment thesecondary side winding T1B may step down the voltage from the primaryside winding T1A from about 60 volts to about 6 volts. This in turn mayreduce the amount of heat that is dissipated from the linear voltageregulator 70. Specifically, the secondary side winding T1B may be usedto step down the voltage from the converter 38 first, before the linearregular 70 further steps down the voltage from the converter 38. Thoseskilled in the art will readily appreciate that the voltage from theconverter 38 may be directly provided to the linear regular 70, howeverthis approach may generate more heat and is not as efficient as theillustrated approach.

The MCU/radio 34 may be supplied low voltage power even if the lightingload 12 is not illuminated. Continuing to refer to both FIGS. 2-3, inone embodiment the MCU/radio 34 may be any type of driver for providingwireless communication of the driver circuit 10, and is in communicationwith the wireless network 16 (FIG. 1). Some examples of wirelesscommunication protocols that the MCU/radio 34 may be compatible withinclude, but are not limited to, Bluetooth®, ZigBee® and 6LoWPAN. Onecommercially available example of the MCU/radio 34 is integrated circuit(IC) model number JN5164, which is commonly used for wirelesscommunication, and is available from NXP B. V., of Eindhoven, theNetherlands. As mentioned above, although a MCU is described, it isunderstood that the disclosure is not limited to an MCU, and anothertype auxiliary circuit or control module may be used as well.

In addition to providing wireless communication, the MCU/radio 34 mayalso be used to provide a digital dimming signal received by the dim pin60 of the main driver 32 if the lighting fixture 14 is ON. Specifically,in one approach the MCU/radio 34 may generate a pulse width modulated(PWM) dimming signal received by the dim pin 60 of the main driver 32through a resistor R3 and a smoothing capacitor C6. The resistor R3 andsmoothing capacitor C6 may smoothen the PWM signal from the MCU/radio 34into a constant voltage signal. In the exemplary illustration as shown,the constant voltage signal may be a constant 0.6 voltage signal. TheMCU/radio 34 generates the PWM dimming signal based on receiving adimming signal received over the wireless network 16 by the user inputdevice 17 (shown in FIG. 1) that is wirelessly connected to theMCU/radio 34 through the wireless network 16.

Referring to FIGS. 1-2, the user input device 17 may be any electronicdevice having wireless capabilities and a user interface 90 for wirelesscontrol of the lighting fixture 14 such as, for example, a remotecontroller, a laptop or tablet computer, or a smartphone. As commonlyknown by those of ordinary skill in the art, the user input device 17may generate the dimming signals sent to the MCU/radio 34 based on anindividual manipulating a dimming slider 92 of the user input device 17.Those of ordinary skill in the art will also appreciate an individualmay turn the lighting fixture 14 ON or OFF by manipulating the buttons94, 96 of the user input device 17 as well. For example, if anindividual selects the ON button 94 of the user input device 17 forturning the lighting fixture 14 ON, then an ON signal may be sent to theMCU/radio 34 though the wireless network 16. Similarly, if an individualselects the OFF button 96 of the user input device 17 for turning thelighting fixture 14 OFF, then an OFF signal may be sent to the MCU/radio34 through the wireless network 16.

The MCU/radio 34 may also control a switch 78 of the driver circuit 10based on the ON signal and the OFF signal being sent to the MCU/radio 34by the user input device 17. In one non-limiting embodiment, the switch78 may be a negative-positive-negative (NPN) transistor such as a BJT.When the lighting fixture 14 is turned OFF and the OFF signal is sent tothe MCU/radio 34 (i.e., the lighting load 12 is not generating light),then a pin 76 of the MCU/radio 34 goes low, thereby turning the switch78 OFF. When the lighting fixture 14 is turned ON, the ON signal is sentto the MCU/radio 34, thereby causing the pin 76 of the MCU/radio 34 togo high and the switch 78 is turned ON.

The integrated switch 78 is connected to a resistor network 80. Theresistor network 80 includes three resistors R4, R5, and R6, where R4and R5 are arranged in a voltage divider. The overvoltage protection pin58 of the main driver 32 is connected to the voltage divider 82 of theresistor network 80. When the switch 78 is ON (and the lighting fixture14 is ON) the resistors R5 and R6 are in parallel with one another.Also, a voltage observed at a node 84 of the resistor network 80 is lessthan an overvoltage value by a threshold amount of voltage. The node 84is located between the resistors R4, R5, and R6. The overvoltage valuerepresents the voltage observed at the overvoltage protection pin 58 ofthe main driver 32 sufficient to trigger the main driver 32 to operateat burst mode of the main driver 32. Since the overvoltage value willtrigger burst mode, it should be understood that the overvoltage valueis selectively generated by the resistor network 80 if the main driver32 is required to operate at burst mode. Burst mode of the main driver32 is explained in greater detail below. For example, in one embodiment,the overvoltage value is about 1.8 volts, and the threshold amount isabout 0.6 volts. Thus, the voltage observed at the node 84 may be about1.2 volts when the switch 78 is ON. The threshold amount may be selectedsuch that the main driver 32 may not be falsely triggered into operatingat burst mode.

Once the switch 78 is deactivated and turned OFF (and the lightingfixture 14 is OFF) the resistor R6 drops out of the resistor network 80,and the voltage at the node 84 rises to a value at or above theovervoltage value. In response to receiving the overvoltage value fromthe resistor network 80, the main driver 32 operates at burst mode.Moreover, once the switch 78 is deactivated, the lighting fixture 14 isOFF and the voltage of the driver circuit 10 at the lighting load 12 maythen drop below a working or forward voltage of the lighting load 12.Those of ordinary skill in the art will readily appreciate the forwardvoltage of the lighting load 12 is the voltage required in order toconduct electricity through the lighting load 12. Thus, if the maindriver 32 controls an output voltage within the driver circuit 10 toprovide the forward voltage to the lighting load 12, then the lightingload 12 will illuminate. Once the output voltage drops below the forwardvoltage, then the lighting load 12 becomes non-conductive, and thelighting load 12 is no longer illuminated. In one embodiment, theforward voltage of the lighting load 12 is about 12 volts.

Burst mode is sometimes referred to as a pulse frequency modulation withan intermittent burst of pulses. Burst mode represents a low powerconsumption mode of the driver circuit 10. Moreover, burst mode may beinitiated by an outside disturbance, and is repeated by a reset of therespective IC (i.e., the main driver 32 in the present embodiment).Those of ordinary skill in the art will readily appreciate that burstmode is generally used in a circuit when the demand for power is low,and the main driver 32 may transition out of burst mode once the demandfor power increases above some threshold. Thus, once the lightingfixture 14 is turned back ON and the voltage required by the lightingload 12 is at or above the forward voltage, then the main driver 32transitions out of burst mode. During burst mode, the main driver 32instructs or controls the switch 31 (FIG. 1) of the main driver 32 tooperate in one or more burst packets. A burst packet is representativeof the switch 31 of the main driver 32 opening and closing once. It isto be appreciated that during burst mode, the voltage produced by thedriver circuit 10 may not rise to the forward voltage of the lightingload 12.

It should also be appreciated that during burst mode, the driver circuit10 may not always operate to sufficiently produce the regulated lowvoltage supplied to the MCU/radio 34. More specifically, during burstmode a frequency of the burst packets may not always be high enough tomaintain a current sufficient to generate the voltage required tooperate the MCU/radio 34. Thus, as described in greater detail below, inresponse to receiving the OFF signal from the user input device 17(FIG. 1) over the wireless signal, the MCU/radio 34 generates aswitching signal sent to the main driver 32. The MCU/radio 34 generatesthe switching signal in a variety of different ways, which is explainedin greater detail below. In response to receiving the switching signalfrom the MCU/radio 34, the main driver 32 increases the frequency of theburst packets such that the driver circuit 10 may generate and maintainthe constant DC voltage required by the MCU/radio 34 during burst mode.In other words, during burst mode the frequency of the burst packets isincreased to a threshold frequency, which in turn causes the switch 31(FIG. 1) of the main driver 32 to open and close at a frequencysufficient to generate the voltage required to operate the MCU/radio 34.

In one embodiment, the switching signal from the MCU/radio 34 may bebased on the PWM dimming signal sent to the main driver 32.Specifically, the MCU/radio 34 includes control logic or circuitry foradjusting the duty cycle of the PWM dimming signal received by the dimpin 60 of the main driver 32 to a threshold duty cycle. Increasing theduty cycle of the PWM dimming to the threshold duty cycle in turn causesthe main driver 32 to increase the frequency of the burst packets duringburst mode such that the driver circuit 10 may generate the constant DCvoltage required by the MCU/radio 34. For example, in one embodiment, ifthe constant DC voltage supplied to the MCU/radio 34 is about 3.3 volts,then the MCU/radio 34 increases the duty cycle of the PWM dimming signalto the threshold duty cycle, which is about eighty percent. This resultsin a voltage ranging from between about 0.7 to about 0.8 observed at thedim pin 60 of the main driver 32.

FIG. 4 is an alternative embodiment of a portion of the driver circuit10, where the switching signal generated by the MCU/radio 34 activates aswitch 102. Similar to the switch 78, in one embodiment the switch 102may also be a NPN transistor such as, for example, a BJT. The switch 102may be in communication with the loop compensation pin 54 of the maindriver 32. More specifically, the switch 102 may be connected to theloop compensation pin 54 of the main driver 32 through a second resistornetwork 104 and a diode D8. The second resistor network 104 includesthree resistors R7, R8, and R9, where the resistors R8 and R9 areconnected in series with one another, and the resistors R7 and R8 arearranged in a voltage divider.

In the embodiment as shown in FIG. 4, the MCU/radio 34 includes a pin106 connected to a base B of the switch 102. When the MCU/radio 34instructs the pin 106 to go low, this in turn will turn the switch 102OFF. When the MCU/radio 34 instructs the pin 106 to go high, this turnsthe switch 102 ON. The MCU/radio 34 may control the switch 102 based onthe user input sent over the wireless network 16 by the user inputdevice 17 (FIG. 1) wirelessly connected to the MCU/radio 34. Morespecifically, in response to receiving the OFF signal over the wirelessnetwork 16, the pin 106 of the MCU/radio 34 goes low, thereby turningthe switch 102 OFF. In response to receiving the ON signal over thewireless network 16, the pin 106 of the MCU/radio 34 goes high, therebyturning the switch 102 ON.

When the switch 102 is ON (and the lighting fixture 14 is ON) thevoltage measured at a node 108 of the second resistor network 104 isless than a second overvoltage value by a second threshold amount ofvoltage. The node 108 is located between the resistors R7 and R8 and acollector C of the switch 102. The second overvoltage value representsthe voltage observed at the loop compensation pin 54 of the main driver32 of the main driver 32 sufficient to increase the frequency of theburst packets to the threshold frequency, which in turn causes theswitch of the main driver 32 to open and close at a frequency sufficientto generate the voltage required to operate the MCU/radio 34. It is tobe understood that the loop compensation pin 54 may represent a pin orother input of the main driver 32 responsible for setting a responsetime of the main driver 32. If the response time of the main driver 32increases, this in turn will also cause the main driver 32 to increasethe frequency of the burst packets during burst mode.

For example, in one embodiment, the second overvoltage value is about2.0 volts, and the second threshold amount is about 0.9 volts. Thus, thevoltage observed at the node 108 of the second resistor network 104 maybe about 1.1 volts when the switch 102 is ON. The threshold amount maybe selected so as to not falsely trigger the main driver 32. However,once the switch 102 is deactivated and turned OFF (and the lightingfixture 14 is OFF), the voltage observed at the node 108 rises to thesecond overvoltage value (e.g., 2.0 volts). Accordingly, the voltageobserved at the loop compensation pin 54 of the main driver 32 rises toa required value. Raising the voltage at the loop compensation pin 54 tothe required value in turn increases the response time of the maindriver 32 such that the frequency of the burst packets is also increasedto the threshold frequency, thereby causing the switch 31 (FIG. 1) ofthe main driver 32 to open and close at a frequency sufficient togenerate the voltage required to operate the MCU/radio 34. Accordingly,the current flowing through the driver circuit 10 generates theregulated low voltage supplied to the MCU/radio 34.

FIG. 5 is yet another embodiment of a portion of the driver circuit 10where the switching signal generated by the MCU/radio 34 activates aswitch 122 in communication with the input pin 50 (V_(CC)) of the maindriver 32. Similar to the switch 78 shown in FIGS. 2-3 and the switch102 in FIG. 4, in one embodiment the switch 122 may also be a NPNtransistor such as, for example, a BJT. The switch 122 may be connectedto the input pin 50 of the main driver 32. More specifically, acollector C of the switch 122 may be connected to the input pin 50 ofthe main driver 32 through the capacitor C1.

In the embodiment as shown in FIG. 5, the MCU/radio 34 includes a pin126 connected to a base B of the switch 122. When the MCU/radio 34instructs the pin 126 to go low, this in turn will turn the switch 122OFF. When the MCU/radio 34 instructs the pin 126 to go high, this turnsthe switch 122 ON. The MCU/radio 34 may control the switch 122 based onthe user input sent over the wireless network 16 by the user inputdevice 17 (FIG. 1). In response to receiving the OFF signal over thewireless network 16, the pin 126 of the MCU/radio 34 goes low, therebyturning the switch 122 OFF. In response to receiving the ON signal fromthe wireless network 16 the pin 126 of the MCU/radio 34 goes high,thereby turning the switch 122 ON. Moreover, as seen in the embodimentof FIG. 5, a resistor R10 may be connected to the output of the EMIfilter 28 (FIG. 2), i.e., the bus voltage +B of the driver circuit 10.

The capacitor C1 may filter voltage received by the resistor R1, whichis connected to the input pin 50 of the main driver 32, when the switch122 is turned on (and the lighting fixture 14 is also turned ON). Thecapacitor C1 may also charge when the when the switch 122 is turned on.However, once the switch 122 is turned OFF (and the lighting fixture 14is also turned OFF) the capacitor C1 is removed from the driver circuit10. This in turn will decrease the overall capacitance observed at theinput pin 50 of the main driver 32. Instead, only the resistor R1 and acapacitor C8 are connected to the input pin 50 of the main driver 32.The voltage at the input pin 50 of the main driver 32 may now increaseand decrease at a quicker rate, since the overall capacitance at theinput pin 50 of the main driver 32 has decreased. Thus, the main driver32 may now reset itself more quickly, which in turn will increase thefrequency of the burst packets to the threshold frequency, which in turncauses the switch 31 (FIG. 1) of the main driver 32 to open and close ata frequency sufficient to generate the voltage required to operate theMCU/radio 34.

The predefined voltage represents the voltage observed at the input pin50 of the main driver 32 sufficient to increase the frequency of theburst packets to the threshold frequency. In one embodiment, thecapacitance of the capacitor C1 is about 0.047 μF, the capacitance ofthe capacitor C8 is about 0.22 μF, and the predefined voltage observedat the input pin 50 is about 12 volts. When the input pin 50 of the maindriver 32 observes the predefined voltage, this in turn may cause a timeconstant τ of the main driver 32 to also increase in value as well.Increasing the time constant τ of the main driver 32 results in the maindriver 32 being reset, and in turn increases the frequency of the burstpackets during burst mode.

FIG. 6 is an exemplary process flow diagram illustrating a method 200 ofproviding constant DC voltage to the MCU/radio 34 once the lightingfixture 14 is turned OFF. Referring generally to FIGS. 1-6, method 200may begin at block 202. In block 202, the MCU/radio 34 monitors thewireless network 16 for the OFF signal from the user input device 17(FIG. 1). As explained above, the OFF signal indicates an individual hasselected the button 96 of the user input device 17 for turning thelighting fixture 14 OFF. Method 200 may then proceed to block 204.

In block 204, in response to receiving the OFF signal from the userinput device 17, the pin 76 of the MCU/radio 34 goes low. This in turnwill turn the switch 78 OFF. Once the switch 78 is turned OFF (and thelighting fixture 14 is OFF) the resistor R6 drops out of the resistornetwork 80, and the voltage at the node 84 rises above the overvoltagevalue, thereby triggering burst mode of the main driver 32. Method 200may then proceed to block 206.

In block 206, the MCU/radio 34 generates the switching signal sent tothe main driver 32, which increases the frequency of the burst packetsto the threshold frequency, thereby causing the switch 31 of the maindriver 32 to open and close at a frequency sufficient to generate theconstant DC voltage required by the MCU/radio 34. As explained above,there are a number of ways to increase the frequency of the switch 31 ofthe main driver 32. Method 200 may then proceed to decision block 208.

In block 208, if the lighting fixture 14 continues to be turned off,then method 200 may return to block 206. However, if the lightingfixture 14 is no longer OFF (i.e., an individual selects the ON button94 of the user input device 17), then method 200 may proceed to block210.

In block 210, the switch 78 is turned ON. Once the switch 78 is ON, thevoltage at the node 84 of the resistor network 80 drops to a voltagevalue (e.g., 1.2 voltage), which is below the overvoltage value (e.g.,1.8 volts) by the threshold amount (e.g., 0.6 volts). Thus, the voltageobserved at the overvoltage protection pin 58 of the main driver 32drops to a value such that the main driver 32 may transition out ofburst mode. Method 200 may then terminate.

Referring generally to the figures, the disclosed driver circuit 10includes a relatively efficient, cost-effective and simple approach forproviding constant DC voltage to an auxiliary circuit (e.g., theMCU/radio 34) without the need for dedicated power circuitry. The drivercircuits currently available typically include a dedicated switched modepower supply for delivering power to the auxiliary circuit, which inturn adds numerous components to the lighting fixture. Moreover, itshould also be appreciated that a dedicated switched mode power supplyalso consumes valuable space within the fixture, and further increasesoverall costs. In contrast, the disclosed driver circuit 10 leveragesthe existing electronic components in order to provide the requiredconstant DC voltage.

While the forms of apparatus and methods herein described constitutepreferred embodiments of this disclosure, it is to be understood thatthe disclosure is not limited to these precise forms of apparatus andmethods, and the changes may be made therein without departing from thescope of the disclosure.

What is claimed is:
 1. A driver circuit receiving wireless communicationover a wireless network, comprising: a lighting load having a forwardvoltage, the lighting load selectively illuminated based on an outputvoltage being provided to the lighting load that is at least the forwardvoltage, wherein the wireless communication is indicative of whether thelighting load is to be illuminated; a main driver for controllingcurrent and voltage within the driver circuit such that when thewireless communication indicates the lighting load is to be illuminated,then the current delivered to the lighting load is regulated by the maindriver, and the output voltage delivered to the lighting load iscontrolled by the main driver is below the forward voltage in responseto the wireless communication indicating the lighting load is not to beilluminated; a switch drivable by the main driver, the main driverdriving the switch at a burst mode in response to receiving anovervoltage value from the driver circuit, wherein the output voltage isless than the forward voltage of the lighting load in response to theswitch operating at the burst mode and the lighting load not beingilluminated; and an auxiliary circuit requiring a substantially constantDC voltage and in communication with the main driver, the auxiliarycircuit receiving the wireless communication over the wireless network,wherein the driver circuit provides the substantially constant DCvoltage at all operating conditions.
 2. The driver circuit of claim 1,wherein the main driver controls the voltage within the driver circuitto provide at least the forward voltage to the lighting load in responseto the wireless communication indicating the lighting load is to beilluminated.
 3. The driver circuit of claim 1, wherein the main drivercauses the switch to operate in at least one burst packet during theburst mode, and wherein the burst packet is representative of the switchopening and closing once.
 4. The driver circuit of claim 3, wherein theauxiliary circuit monitors the wireless network for an OFF signal. 5.The driver circuit of claim 4, wherein the auxiliary circuit induces aswitching signal at an OFF input of the main driver in response toreceiving the OFF signal over the wireless network.
 6. A driver circuitreceiving wireless communication over a wireless network, comprising: alighting load having a forward voltage, the lighting load selectivelyilluminated based on an output voltage being provided to the lightingload that is at least the forward voltage, wherein the wirelesscommunication is indicative of whether the lighting load is to beilluminated; a main driver for controlling voltage within the drivercircuit such that when the wireless communication indicates the lightingload is to be illuminated, then the output voltage provided to thelighting load is at least the forward voltage, and the voltage deliveredto the lighting load is below the forward voltage in response to thewireless communication indicating the lighting load is not to beilluminated; a switch drivable by the main driver, the main driverdriving the switch at a burst mode in response to receiving anovervoltage value from the driver circuit, wherein the output voltage isless than the forward voltage of the lighting load in response to theswitch is operating at the burst mode and the lighting load not beingilluminated; and an auxiliary circuit requiring a substantially constantDC voltage and in communication with the main driver and receives thewireless communication over the wireless network, wherein the drivercircuit provides the substantially constant DC voltage at all operatingconditions.
 7. The driver circuit of claim 6, wherein the main driverregulates current to the lighting load in response to the wirelesscommunication indicating the lighting load is to be illuminated.
 8. Thedriver circuit of claim 6, wherein the main driver causes the switch tooperate in at least one burst packet during the burst mode, and whereinthe burst packet is representative of the switch opening and closingonce.
 9. The driver circuit of claim 8, wherein the auxiliary circuitmonitors the wireless network for an OFF signal.
 10. The driver circuitof claim 9, wherein the auxiliary circuit induces a switching signal atan OFF input of the main driver in response to receiving the OFF signalover the wireless network.
 11. A driver circuit receiving wirelesscommunication over a wireless network, comprising: a lighting loadhaving a forward voltage, the lighting load selectively illuminatedbased on an output voltage being provided to the lighting load that isat least the forward voltage of the lighting load, wherein the wirelesscommunication is indicative of whether the lighting load is to beilluminated; a switch; a network that selectively generates anovervoltage value; a main driver including a plurality of inputs, themain driver in communication with the switch and the network, the maindriver causing the switch to operate in burst packets at a burst mode inresponse to receiving the overvoltage value from the network, the maindriver controlling voltage to the lighting load such that when thewireless communication indicates the lighting load is not to beilluminated then the forward voltage is not provided to the lightingload and the lighting load is not illuminated; and an auxiliary circuitrequiring a substantially constant DC voltage, wherein the auxiliarycircuit is in communication with the main driver and receives thewireless communication over the wireless network, the auxiliary circuit:monitoring the wireless network for an OFF signal; and inducing aswitching signal at one of the plurality of inputs of the main driver inresponse to receiving the OFF signal over the wireless network, and inresponse to receiving the switching signal the main driver increases afrequency of the burst packets to a threshold frequency to generate theconstant DC voltage required by the auxiliary circuit during burst mode.12. The driver circuit of claim 11, wherein the switch is part of themain driver.
 13. The driver circuit of claim 11, wherein the switch islocated external to the main driver.
 14. The driver circuit of claim 11,wherein the switch is a metal-oxide-semiconductor field-effecttransistor (MOSFET).
 15. The driver circuit of claim 11, wherein thenetwork includes a first resistor, a second resistor, a third resistor,and a node located between the first resistor, the second resistors, andthe third resistor, and wherein the first resistor and the secondresistor are arranged in a voltage divider.
 16. The driver circuit ofclaim 15, comprising a second switch, the third resistor drops out ofthe network and the voltage at the node rises to a value at or above theovervoltage value in response to the second switch being turned OFF. 17.The driver circuit of claim 11, wherein at least one of the main driverand the auxiliary circuit are connected to a floating ground.
 18. Thedriver circuit of claim 11, wherein at least one of the main driver andthe auxiliary circuit are connected to a common ground of the drivercircuit.
 19. The driver circuit of claim 11, wherein the auxiliarycircuit is in communication with a second switch, and in response to thesecond switch being turned OFF the network generates the overvoltagevalue.
 20. The driver circuit of claim 11, wherein the lighting load isa light emitting diode (LED).
 21. The driver circuit of claim 11,wherein the lighting load includes a forward voltage of about 12 volts.22. The driver circuit of claim 11, wherein the main driver is for lightemitting diode (LED) dimming control, and wherein one of the pluralityof inputs of the main driver includes a dimming input.
 23. The drivercircuit of claim 22, wherein the auxiliary circuit generates apulse-width modulated (PWM) signal received by the dimming input of themain driver.
 24. The driver circuit of claim 23, wherein the auxiliarycircuit increases the duty cycle of the PWM signal to a threshold dutycycle, and wherein increasing the duty cycle of the PWM signal to thethreshold duty cycle causes the main driver to increase the frequency ofthe burst packets during burst mode such that the driver circuitgenerates the constant DC voltage.
 25. The driver circuit of claim 11,wherein the auxiliary circuit is in communication with a second switch,and wherein the second switch is in communication with a loopcompensation input of the main driver.
 26. The driver circuit of claim25, wherein the voltage at the loop compensation pin rises to a requiredvalue to increase a response time of the main driver such that the maindriver increases the frequency of the burst packets to the thresholdfrequency in response to the second switch being turned OFF.
 27. Thedriver circuit of claim 11, wherein the auxiliary circuit is incommunication with a second switch, and wherein the second switch is incommunication with a power input of the main driver through a capacitor.28. The driver circuit of claim 27, wherein the capacitor charges inresponse to turning the second switch OFF, and the capacitor is removedfrom the driver circuit in response to turning the second switch ON.